In prior art, there exists a bluetooth headset, which is used together with a mobile phone and is mainly composed of a transceiver and an acoustic generator which are connected by a piece of lead. The transceiver and the acoustic generator are firmly connected and can be integrally made. The transceiver has a hook that can be hung on ears; while being used, the hook is hung on ears and the acoustic generator is only in earholes. The transceiver is used for receiving and transmitting information and can convert the received information into audio signals and then transmit them to the acoustic generator through lead to generate sound; since the bluetooth headset is just hung on ears while being used, it can't be firmly fixed, it may easily fall, particularly under movement states, such as walking, riding and head turning, the headset will be dropped more easily and it will be lost; after it has been used for long time, the ears will be in pain; moreover, the existing bluetooth headset is designed to have only a single track, so the sound is not clear while in use and easy to be disturbed by external noises.
In prior art, there exists another kind of cap, which mainly includes a cap body and in particular has the function of retaining and keeping out sunshine, but it also has a shortcoming, that is, it has a relatively single use function.